An electric fuel pump having a pump section and a motor section within a case member is, for example, described in US Patent Application Publication No. 2008/0063545 (JP-A-2008-64027, JP-A-2008-64029). In such a fuel pump, fuel is suctioned from a fuel suction portion of the pump section. The fuel is increased in pressure through the pump section, and then flows through a peripheral area of the motor section. Then, the fuel is discharged to the outside of the fuel pump from a discharge port of a discharge-side cover disposed on an end of the motor section opposite to the pump section.
The pump section is supplied with electric power from an external power source through a terminal. The electric power supplied to the terminal is supplied to the motor section through brushes and a commutator. The fuel pump described in US2008/0063545 is adapted to be used in a gasoline-alternate fuel.
The gasoline-alternate fuel, such as high density alcohol fuel, bio-ethanol, ethanol 100% fuel and the like, has been recently in great demand. The gasoline-alternate fuel is hereinafter referred to as alcohol mixture fuel. The alcohol mixture fuel has electric conductivity higher than that of general fuel such as gasoline. In the fuel pump for the alcohol mixture fuel, therefore, it is required to restrict an electrical short circuit between a positive electrode terminal and a negative electrode terminal through the fuel when voltage is generated between the terminals and electrochemical corrosion of the terminals due to the terminals being exposed in the fuel.